A liquid-crystalline polyester resin, which retains excellent fluidity, mechanical strength, heat resistance, chemical resistance, electric properties and the like in a good balance, is widely used as a high performance engineering plastic, and is mostly used for injection molding.
The liquid-crystalline polyester resin, which has recently often a further advanced and specialized application, is expected to be molded efficiently and economically by blow molding and the like, particularly by extrusion molding to get an article with excellent physical properties of liquid-crystalline polyester retained.
For example, pipes, containers and the like, which is needed to have high mechanical properties in addition to heat resistance to use under a high temperature atmosphere, have conventionally been made of metal materials, but are desired to be made of the liquid-crystalline polyester resin described above by extrusion-molding in order to furnish them with light weight and corrosion resistant at a low cost. However, the liquid-crystalline polyester resin, which is low in melt tension as the most important property for applying to blow molding in spite of excellent fluidity and physical properties, is so remarkably ready at drawdown that it is quite difficult to use for blow molding to get a desired shape of molded article. There have been contemplated various methods to improve, for example, a method using a highly polymerized polyester resin with a high intrinsic viscosity, a method using a branched polyester, and a method for further supplying the polyester resin with various fillers. But any methods give little improvements, and thus are insufficient to use the polyester resin.
For example, JP-A 6-306261 discloses a liquid-crystalline polyester resin composition for blow or extrusion molding which is produced by formulating and melt-kneading (A) 100 parts by weight of an aromatic liquid-crystalline polyester containing a specific construction unit, (B) 0.2-10 parts by weight of a styrene copolymer consisting of 40-97 wt % of styrene, 60-3 wt % of glycidyl ester of α,β-unsaturated acid and 0-50 wt % of the other vinyl monomer and (C) 0-100 parts by weight of one or more of fibrous, powdery and tabular fillers to improve the melt tension of a liquid crystal resin, thereby to prevent parison drawdown (see claims 1 to 5 of JP-A 6-306261).
However, those different resin components to improve the melt tension cannot be applied to the molded article requiring a strict performance, because they deteriorate performances of the liquid crystalline resin composition such as heat resistance, mechanical strength and gas permeability which are reflected.
JP-A 8-311311 discloses an aromatic polyester composition containing (A) 100 parts by weight of an aromatic polyester, having a melt viscosity of 10 and 15,000 poise as measured at a shear rate of 1000/sec at a temperature of 40° C. higher than the temperature at which the aromatic polyester starts to show its anisotropy (a temperature for initiating liquid crystal), selected from three kinds of aromatic polyesters consisting of specific construction units and (B) 0.1-60 parts by weight of a copolymer consisting of α-olefins and the glycidyl ester of α,β-unsaturated acid (JP-A 8-311311 (see claim and paragraphs [0001], [0024] and [0048]).
JP-A 8-301983 discloses a blow molded container made of a liquid-crystalline polyester resin composition, containing (A) 56.0-99.0 wt % of liquid-crystalline polyester and (B) 44.0-1.0 wt % of an epoxy group-containing ethylene copolymer, (B) consisting of (a) 50.0-99.9 wt % of an ethylene unit, (b) 0.1-30.0 wt % of an unsaturated carboxylic acid glycidyl ester unit or an unsaturated glycidyl ether unit and (c) 0-49.9 wt % of an ethylene base unsaturated ester unit (JP-A 8-301983 (see claims 1 to 7).
JP-A 9-12744 discloses a liquid-crystalline polyester resin composition film obtained by tubular film extrusion molding a liquid-crystalline polyester resin composition containing (A) a liquid-crystalline polyester in the continuous phase and (B) a thermoplastic resin in the dispersed phase, wherein the liquid-crystalline polyester resin composition has a melt viscosity ratio (viscosity 2/viscosity 1) of 0.1 and 0.7, and has a flow beginning temperature (FT1) to satisfy FT1>FT2-10 in relation to the flow beginning temperature (FT2) of the liquid-crystalline polyester (A), wherein the flow beginning temperature (FT1) is defined as a temperature (° C.) at which the melt viscosity of a resin is 48,000 poises when the resin heated at a temperature-programmed rate of 4° C./min is extruded through an 1 mm inside-diametric and 10 mm long nozzle under a load of 100 kgf/cm2; the viscosity 1 is a melt viscosity which the resin has when measured at a shear rate of 100/sec or 1000/sec at the flow beginning temperature; and the viscosity 2 is a melt viscosity which the resin has when measured at the same shear rate at a temperature of 20° C. higher than the flow beginning temperature.
However, all three technologies described above relate to aromatic polyester liquid crystalline resins, but give neither description nor suggestion about a wholly aromatic polyesteramide liquid crystalline resin.